S u m m a r y :Both obesity and lower body weight increase the risk of dementia, suggests a new study that links high and low BMIs (body mass index) with a greater likelihood for the neurodegenerative disease. The findings are published in the Alzheimer’s & Dementia journal.

The Harms of Abnormal BMIs

Obesity has been associated with a number of ills in a growing body of research; high BMIs are associated with health issues like heart disease, hypertension, diabetes, and even some cancers. On the other hand, BMIs that are below the normal range are also problematic. A recent study, conducted by a team from the University College London (UCL), links abnormal BMIs with dementia. Based on data gathered from 1.3 million adults from Europe and the US, the findings indicate that high BMIs are ultimately linked with a higher dementia risk, and that the onset of the disease tends to be associated with lower body weights.

“The new study confirms both the adverse effect of obesity as well as weight loss caused by metabolic changes during the pre-dementia stage,” says lead author, UCL’s Mika Kivimäki.

The BMI-Dementia Link

Previous studies demonstrate the same seemingly contradicting links. Some research works suggest that obesity leads to a higher dementia risk while others associate lower weight to a greater incidence of the condition. The new study might have reconciled between the diverging opinions.

The BMI-dementia dynamics appear to follow a certain pattern: generally, dementia patients are found to have been overweight decades before they develop the disease, and when they reach near to the onset of dementia, they display a lower BMI than their healthy counterparts.

“The BMI-dementia association observed in longitudinal population studies, such as ours, is actually attributable to two processes,” explains Kivimäki. “One is an adverse effect of excess body fat on dementia risk. The other is weight loss due to pre-clinical dementia. For this reason, people who develop dementia may have a higher-than-average body mass index some 20 years before dementia onset, but close to overt dementia have a lower BMI than those who remain healthy.”

BMI & Dementia in Figures

Two decades before the symptoms of dementia appear, higher BMI predicts its occurrence. Every 5-unit BMI increase is linked with a 16-33% greater dementia risk.

On the other hand, the pre-clinical phase nearing to the onset of dementia is linked with a lower BMI.

Future Hope?

This study indicates that dementia might be prevented or delayed bymaintaining a healthy weight.